The present invention relates to the connection of conduits and the like. More particularly, the present invention relates to the connection of tubular sections in subsea environments and, especially, to the laying or repairing of underwater pipelines such as are used in the transmission of oil and gas from offshore production facilities to onshore storage or treatment facilities.
The laying or repairing of underwater pipelines is, at best, a hazardous, difficult, and expensive operation. In general, many techniques applicable to the laying or repairing of surface or underground pipelines are not practical in such underwater environments. For example, it is common practice in laying surface pipelines to connect adjacent sections of the pipelines by first securing pipe flanges to the adjacent pipe sections followed by bolting the flanges together to bring mating surfaces of the flanges into sealing engagement. Even in laying surface or underground pipelines, connection of pipeline sections using such conventional bolted flanges is time consuming. In underwater environments, it will readily be appreciated that the use of such bolted flanges presents a most difficult if not impossible task.
While conventional welding techniques can be employed to connect adjacent pipeline sections, it is usually necessary to provide an evacuated chamber around the area to be welded, the chamber serving to provide a suitable working environment to carry out the welding. Such chambers, besides being expensive, are difficult to control, and therefore dangerous, and in many cases their use is impractical or impossible.
A problem frequently encountered in the laying or repairing of underwater pipelines is misalignment of adjacent sections of the pipeline which are to be joined. Such misalignment can be caused by undulations on the ocean floor, mishandling of the pipe sections, etc. Such misalignment poses a particularly difficult problem when a section of submerged pipeline is being repaired. As is well known, if a submerged pipeline becomes damaged, it is necessary to either raise the pipeline to the surface and repair the damaged section or effect some kind of subsea repair. In either event, it is generally necessary to remove the damaged section of pipe. If a subsea repair is attempted, it is extremely difficult to provide a repair section of exactly the proper length to replace the damaged section which has been removed.